Ectrostatic image forms a developable image in a silver salt

ABSTRACT

A process of rendering visible electrostatic charge patterns is described. The process involves the formation of a charge pattern on a charge-retaining member which is then placed in contact with an unexposed silver salt-containing element to form a latent image on the element which is then processed by standard photographic techniques to form a visible silver image. The process eliminates detrimental solvent and abrasive action which occur in standard electrophotographic development techniques.

United States Patent 11 1 Gilman, Jr. et al.

[ LATENT ELECTROSTATIC IMAGE FORMS A DEVELOPABLE IMAGE IN A SILVER SALT 751 Inventors: Paul B. Gilma n, Jr.; Joseph Y. Kaukeinen, both of Rochester, NY.

[73] Assignee: Eastman Kodak Company,

Rochester, NY. V

21 Appl. No.: 264,214

Related u.s. Application Data [63] Continuation-in-part of Ser. No. 887,411, Dec. 22,

[52] U.S. Cl. 96/1 R, 96/1.5, 96/27 R, 96/50 R, 96/68, 250/652, 250/49.5 ZC, 96/1 E [51] Int. Cl. G03g 13/22, G03c 5/00 [58] Field of Search... 96/1 R, l E, 27, 1 96/38.4, 68, 69

[56] References Cited UNITED STATES PATENTS 2,939,787 6/1960 Giaimo 96/1 R 3,457,072 7/1969 Ditzer et al...... 96/68 X 3,157,500 11/1964 Abbott et a1 96/27 R X FOREIGN PATENTS OR APPLICATIONS 1,098,302 1/1968 Great Britain 96]! E Jan. 8, 1974 OTHER PUBLICATIONS Effect of Electrical Discharges on Photographic Layers, Baier, Bild & Ton, March 9, 1956, pp. 70-71. Image Conversion and Recording With a Silver Emulsion-Photoconductor System, Somers, PSE, Vol. 10, No. 1, Jan.-Feb.1966 pp. 30-34.

Photographic Data Recording By Direct Exposure With Electrons," Tarnowski et al., Journ. SMPTE,

V01. 71, Oct. 1962, pp. 765-768.

Primary Examiner-R0land E. Martin, Jr. Attorney-Robert W. Hampton et al.

57 ABSTRACT tographic techniques to form a visible silver image.

The process eliminates detrimental solvent and abrasive action which occur in standard electrophotographic development techniques.

14 Claims, N0 Drawings 1 LATENT ELECTROSTATIC IMAGE FORMS A DEVELOPABLE IMAGE INA SILVER SALT This is a continuation-in-part application based on US. Pat. Ser. No. 887,411, filed Dec. 22, 1969.

This invention relates to the art of electrography and more particularly to novel electrophotographic imag ing processes.

Electrophotographic imaging processes and techniques havebeen extensively described in both the patent and other literature: see, for example, US. Pat. No. 2,221 ,776; 2,277,013; 2,297,691; 2,357,809; 2,551,582; 2,825,814; 2,833,648; 3,220,324; 3,220,831; 3,220,833; and many others. Electrophotographic elements utilized intheabove processes typically involve an electrically conducting support on which is coated aphotoconductive insulating material. This material is given an over-all surface charge by suchmeans as subjecting it to a corona discharge while maintained in darkness. The charged element isthen given an imagewise exposure to'actinic radiation which discharges the photoconductor in the exposed areas to produce an electrostatic charge pattern. This charge pattern, as well as electrostatic charge patterns produced by other techniques, can be rendered visible by a development step in which the chargedsurface of the photoconductive element is brought into contact with a suitable developer composition.

Conventional dry developers typically include a carrier that can either be a magneticmaterial such asiron filings, etc., or a triboelectrically chargeable nonmagnetic substance such as glass beads, etc. In addition to the carrier, suitable developers contain an electroscopic toner material which is typically formed of a resinous material which can becolored or darkened for purposes of visibility. Another useful development means involves a liquid developer which is typically comprised of an insulating carrier liquid havingdispersed thereinmarki'ng particlesformed of a resin and colorant. In all such previous development systems, the

developer marking particles are physically attracted to the charged surface of the element adhered thereto. This resultsin the formation of a visible image which is essentially of the same quality as the electrostatic charge image. Thus, if a photoconductor used has a slow photographic speed such that small differences in charge are produced, present development techniques cannot increase the effective speed. An additional problem encountered with such prior development techniques is that the solvent and abrasive action of the developer on the sensitive'layer tend to reduce the usefull life 'of a photoconductive element.

Accordingly, there is a need in the art for means of increasing the effective speedof photoconductive systems. Similarly, there is a need forsuitable developmerit techniques which eliminate solvent and abrasive action on the photoconductive element.

It is; therefore,an object of this invention to provide novel means forrendering electrostatic charge patterns imaging means forobtaininghigher effective photoconductivespeeds.

It is a further object of this invention to provide a novel imaging method for use with photoconductive elementswhich eliminatesadverse solvent and abrasive damage to the element.

These and other objects and advantages are accomplished in accordance withthisinvention by placing a charge-bearing member carrying an electrostatic charge pattern in contact with a silver salt layer. A latent image is thereby formed in the silver salt layer which can be developed to produce a visible image. The various techniques known in the silver halide art can 'be employed to produce higher effective speeds during chemical development of the latent image.

ln accordance with this invention, an electrostatic charge pattern is produced on a charge-bearing memher by any of the suitable techniques known in the art of electrography. One particularly useful means of producing such charge patterns isby electrophotographic techniques. Electrophotography involves the use of a sensitive member typically comprised of a conducting support having coated thereon a layer of a photoconductive composition.

Suitable supporting materials for use in members of the type described above can include any of a wide variety of electrically conducting supports, for example, paper (at a relative humidity above 20 per cent), aluminum foil-paper laminates; metal foils such as aluminum foil, zinc foil, etc.; metal plates, such as aluminum, copper, zinc, brass and galvanized plates; vapor-deposited metal layers such as silver, nickel, aluminum and the like, coated on paper or conventional photographic film bases such as cellulose acetate, polystyrene, poly- (ethylene terephthalate), etc. Such conducting materials as nickel can be coated by vacuum deposition on transparent film supports in sufficiently thin layers to allow electrophotographic members prepared therewith to be .exposedfrom either side of such members. An especially useful conducting support can be prepared by coating a support material such as poly(ethylene terephthalate) with a conducting layer containing a semiconductor such as cuprous iodide dispersed in a resin. Such conducting layers both with and without insulating barrier layers are described in US. Pat. No. 3,245,833 and 3,428,451. Likewise, a suitable conductingcoating can be prepared from the sodium salt of a carboxyester lactone of maleic anhydride and a vinyl acetate polymer. Such kinds of conducting layers and methods for their optimum preparation and use are disclosed in US. Pat. No. 3,007,901 and 3,267,807.

The photoconductive compositions which can be coated on the above supports include a wide variety of materials. Usefulcompositio'ns typically comprise a photoconductive compound in anelectrically insulating, film-forming resin binder. Both inorganic and organic photoconductors can be used in the present invention as well as mixtures of two or more photoconductors. Suitable inorganic photoconductors include zinc oxide, cadmium sulfide, cadmium selenide, titanium dioxide and others. Useful-organic photoconductors include the following materials:

A. Arylamine photoconductors.itncluding substituted and unsubstituted arylamines, diarylamines, nonpolymeric triarylamines and polymeric triarylamines such as those described in U. 5. Pat. No. 3,240,597 and 3,180,730.

B. Photoconductors represented by the formula Lilla where Z and Z are aromatic radicals, Q is a hydrogen atom or an aromatic amino group, such as Z'NH; b is an integer from 1 to about 12, and L is a hydrogen atom or an aromatic radical, these materials being more fully described in U. S. Pat. No. 3,265,496.

C. Polyarylalkane photoconductors including leuco bases of diary] or triarylmethane dye salts, 1,1,1- triarylalkanes wherein the alkane moiety has at least two carbon atoms and tetraarylmethanes having an amino group substituted in at least one of the aryl nuclei attached to the alkane and methane moieties of the latter two classes of photoconductors which are non-leuco base materials; and also other polyarylalkanes included by the formula:

wherein each of D, E and G is an aryl group and J is a hydrogen atom, an alkyl group, or an aryl group, at least one of D, E and G containing an amino substituent, these materials being more fully described in U. S. Pat. No. 3,274,000, French Pat. No. 1,383,461 and in u. 5. Pat. No. 3,542,544 by Seus and Goldman.

D. Photoconductors comprising 4-diarylamino substituted chalcones having the formula:

wherein R and R are each phenyl radicals including substituted phenyl radicals, these materials being more fully described in Fox U. S. Pat. No. 3,526,501 and other chalcones as disclosed in U. S. Pat. No. 3,265,497.

E. Non-ionic cycloheptenyl compounds which may be substituted with substituents such as aryl, hydroxy, azido, nitrogen heterocycles, or oxycycloheptenyl; these compounds being more fully described in U. S. Pat. No. 3,533,786, issued Oct. 13, 1970.

F. Compounds containing an nucleus, including N,N-bicarbazyls 2,563,785; tetrasubstituted hydrazines, which compounds are more fully described in U. S. Pat. No. 3,542,546, issued Nov. 24, 1970.

G. Organic compounds having 'a 3,3'-bis-aryl-2- pyrazoline nucleus which is substituted in either five-member ring with the same or different substituents. These organic photoconductors are more fully described in U. S. Pat. No. 3,527,602, issued Sept. 8, 1970.

H. Triarylamines in which at least one of the aryl radicals is substituted by an active hydrogencontaining group or a vinyl or vinylene radical having at least one active hydrogen-containing group. These materials are more fully described in U. S. Pat. No. 3,567,450, issued Mar. 2, 1971 and U. S. Pat. No. 3,658,520, issued Apr. 25, 1972.

p-diethylaminophenylarsine Organo-metallic ompounds having at least one amino-aryl substitutent attached to a Group lVa or Group Va metal atom such as silicon, germanium, tin and lead from Group lVa and phosphorus, arsenic, antimony and bismuth from Group Va. These materials can be substituted in the metallo nucleus with a wide variety of substituents but at least one of the substituents must be an amino-aryl radical. These materials are described in U. S. Pat. No. 3,647,429, issued Mar. 7, 1972.

J. Polymeric organic photoconductors such as poly- N-vinylcarbazoles and related vinyl polymers, such materials being disclosed, for example, in U. S. Pat. No. 3,037,861, U. S. Pat. No.3,155,503, U. S. Pat. No. 3,418,116, U. S. Pat. No. 3,421,891 and U. S. Pat. No. 3,232,755.

K. Any other organic compound which exhibits photoconductive properties such as those set forth in Australian Pat. No. 248,402.

Representative organic photoconductors useful in this invention include the compounds listed below:

TABLE I diphenylamine dinaphthylamine N,N-diphenylbenzidine N-phenyl-l-naphthylamine N-phenyl-Z-naphthylamine N,N-diphenyl-pphenylenediamine 2-carboxy-5-chloro-4-methoxydiphenylamine p-anilinophenol N,N'-di-2-naphthyl-p-phenylenediamine 4,4-benzylidene-bis-(N,N-dimethyl-m-to1uidine) triphenylamine N,N,N',N-tetraphenyl-m-phenylenediamine 4-acetyltriphenylamine 4-hexanoyltriphenylamine 4-lauroyltriphenylamine 4-hexyltriphenylamine 4-dodecyltriphenylamine 4,4-bis(dipheny1amino)benzil 4,4-bis(dipheny1amino)benzophenone polyadipyltriphenylamine polysebacyltriphenylamine polydecamethylenetriphenylamine poly-N-( 4-vinylphenyl )diphenylamine poly-N-(vinylphenyl)a,a-dinaphthylamine 4,4'benzylidene-bis( N.N-diethyl-m-toluidine) 4',4' -diamino-4-dirnethylamino-2,2"-dimethyltriphenylmethane 4',4"-bis(diethylamino)-2,6-dichloro-2,2 -dimethyltriphenylmethane poly-N-vinylcarbazole brominated-N-vinylcarbazole 4,4"-bis(diethylamino)-2,2'f-dimethyldiphenylnaphthylmethane 2,2"-dimethyl-4,4',4' '-tris(dimethy1amino)triphenylmethane 4',4"-bis( diethylamino)-4-dimethylamino-2',2

dimethyltriphenylmethane 4,4-bis(diethylamino )-2-ch1oro-2,2' '-dimethyl-4- dimethylaminotriphenylmethane 4',4' '-bis(diethylamino)-4-dimethylamino-2,2',2

trimethyltriphenylmethane 4-hydroxytriphenylamine Z-hydroxytriphenylamin 4-formyltriphenylamine oxime 4-acetyltriphenylamine oxime l-( p-diphenylaminophenyl)hexanol 1-( p-diphenylaminophenyl)dodecanol p-diphenylaminobenzoic acid anhydride 4-cyanotriphenylamine p-diphenylaminobenzoic acid N,N-diphenylamide p-diphenylaminobenzoic acid p-diphenylaminobenzoyl chloride 3-p-diphenylaminophenylpropionic acid 4-formyltriphenylamine semicarbazone triphenyl-p-diethylaminophenylsilane methyl-diphenyl-p-diethylaminophenylsilane triphenyl-p-diethylaminopheny-lgermane triphenyl-p-dimethylaminophenylstannane triphenyl-p-diethylaminophenylstannane diphenyl-di-(p-diethylaminophenyl)stannane triphenyl-p-diethylaminophenylplumbane tetra-p-diethylaminophenylplumbane phenyl-di-(p-diethylaminophenyl)phosphine bis(p-diethylaminophenyl)phosphine oxide tri-p-dimethylaminophenylarsine tri-p-diethylaminophenylarsine 2-methyl-4-dimethylaminophenylarsine oxide tri-p-diethylaminophenylbismuthine methyl-di-(p-diethylaminophenyl)arsine methyl'di-(p-diethylaminophenyl)phosphine phenyl-tri-(p-diethylaminophenyl)stannane methyl-tri-(p-diethylaminophenyl)stannane tetra-p-diethylaminophenylgermane diphenyl-p-diethylaminophenylsilane P-diethylaminophenylarsine tetrakis-[diphenyl-(p-diethylaminophenyl)plumblylmethane tetrakis-[diphenyl-(p-diethylaminophenyl)stannyl]- stannane bis-[phenyl-(p-diethylaminophenyl)]dibismuthine tri(p-diethylaminophenyl)phosphine sulfide di(p-diethylaminophenyl)thioxotin Although some polymeric organic photoconductors can be coated on a support without being blended with resinous binder materials, it is usually necessary or at least desirable to blend organic as well as inorganic photoconductors with a resinous. or plastic material which serves as a matrix or binder'for coating the photoconductor on its support. The photoconductive element or layer thus would include both the active organic or inorganic photoconductor and the resinous binder, if one is used.

Preferred binders for use in preparing the present photoconductive layers are film-forming, polymeric binders having fairly high dielectric strength which are good electrically insulating film-forming vehicles. Materials of this type comprise styrene-butadiene copolymers; silicone resins; styrene-alkyd resins; siliconealkyd resins; soya-alkyd resins; poly(vinyl chloride); poly(vinylidene chloride); vinylidene chloride acrylonitrile copolymers; poly(vinyl acetate); vinyl acetatevinyl chloride copolymers; poly(vinyl acetals), such as poly(vinyl butyral); polyacrylic and methacrylic esters, such as poly(methyl methacrylate), poly(n-butyl methacrylate), poly(isobutyl methacrylate), etc; polystyrene; nitrated polystyrene; poly(methyl styrene); isobu' tylene polymers; polyesters, such as copoly[ethyleneco-alkylenebis(alkyleneoxyary1)- phenylenedicarboxylate], e.g., poly[ethylene-coisopropylidene-2,2-bis( ethyleneoxyphenyl )terephthalate]; phenolformaldehyde resins; ketone resins; polyamides; polycarbonates; polythiocarbonates; copolymers of vinyl haloarylates and vinyl acetate such as poly( vinyl-m-bromobenzoate-co-vinyl acetate); waxes and chlorinated polyethylene.

Solvents useful for preparing coating compositions with the photoconductors of the present invention can include a wide variety of organic solvents for the components of the coating composition. For example, benzene; toluene; acetone; Z-butanone; chlorinated hydrocarbons such as methylene chloride, ethylene chloride and the like; ethers, such as tetrahydrofuran and the like, or mixtures of such solvents can advantageously be employed in the practice of this invention.

In preparing the coating compositions useful results are obtained where the photoconductor substance is an amount equal to at least about 1- weight percent of the coating composition. The upper limit in the amount of photoconductor substance present can be widely varied in accordance with the .usual practice. In those cases where a binder is employed, it is normally required that the photoconductor substance be present in an amount from about 1 weight percent of the coating composition to about 99 weight percent of the coating composition. A preferred weight range for the photoconductor substance in the coating composition is from about 10 weight percent to about weight percent.

Sensitizing compounds useful with the described photoconductive elements can be selected from a wide variety of materials, including such materials as pyrylium dye salts including thiapyrylium dye salts and selenapyrylium dye salts disclosed in VanAllan et al. U. S. Pat. No. 3,250,615; fluorenes, such as 7,12-dioxo-1 3- dibenzo(a,h)fluorene, 5,l0-dioxo-4a,l 1- diazabenzo(b)fluorene, 3,13-dioxo-7- oxadibenzo(b,g)fluorene, and the like; aggregate-type sensitizers of the type described in US. Pat. Nos. 3,616,396, 3,616,414, 3,616,415, 3,616,418; aromatic nitro compounds of the kind described in U. S. Pat. No. 2,610,120; anthrones like those disclosed in U. S. Pat. No. 2,670,284; quinones, U. S. Pat. No. 2,670,286; benzophenones, U. S. Pat. No. 2,670,287; thiazoles, U. S. Pat. No. 2,732,301; mineral acids; carboxylic acids, such as maleic acid, diand trichloroacetic acids, and salicylic acid; sulfonic and phosphoric acids; and other electron acceptor compounds as disclosed by H. Hoegl, J. Phys. Chem, 69, No. 3, 755-766(March 1965), and U. S. Pat. No. 3,232,755.

The amount of sensitizer that can be added to a photoconductor layer to give effective increases in speed can vary widely. The optimum concentration will vary with the specific photoconductor and sensitizing compound used. ln general, substantial speed gains can be obtained where an appropriate sensitizer is added in a concentration range from about 0.0001 to about 10 weight percent or more based on the weight of the coating composition. Normally, sensitizers are added to the coating composition in an amount of about 0.005 to about 5.0 percent by weight of the total coating composition.

In general, the sensitive members of the type described above can be employed in any of the wellknown electrophotographic processes which require photoconductive layers. In one process of this type, an electrophotographic member is held in the absence of actinic radiation and given a blanket electrostatic charge by placing it under a corona dischargeThis uniform charge is retained by the sensitive layer because of the substantial dark insulating property of the layer, i.e., thelow conductivity of the layer in the absence of actinic radiation. The electrostatic charge formed on the surface of the photoconductive layer is then selectively dissipated from the surface of the layer by imagewise exposure to actinic radiation by means of a con tern of electrostatic charge is formed by virtue of the fact that radiation striking the photoconductorcauses the electrostatic charge in the exposed areas to be con ducted awayifrom the surface in proportion to themtensity of the radiation in a particular area. The electrostatic charge pattern produced as above can be used directly or the-pattern can be placed on an insulating sheet by charge transfer procedures. Of course, other procedures can be used to prepare charge patterns on nonsensitive charge-bearing members such as insulating sheets of, for example, poly(ethylene terephthalate) orinsulator-coated paper, etc. In the'latter instance, the resultantcharge pattern need not bekept in darkness prior to use.

Now in accordance with the presentinvention, the electrostaticimage+bearingmember is placed in facetogface contact with a silver salt-bearing surface of a silver salt element. Suitable elements are typicallycomprised of awsupport carrying a light-sensitive silver halideglayer or a layer of another light-sensitive silver salt such as silver behenate, etc. Useful support materials include ,paper, cellulose acetate, polystyrene, poly- (ethylenetterephthalate), glass and the like. The silver halide layer, carried on the support can be in the form of, .for example, a silver halide emulsion of the type now welLknown in the art of photography. Emulsions ofthis type are generally comprised of a gelatin or other hydrophilic colloid binder having silver halide suspended therein. The silver halides usefulin this invention include silver chloride, silver bromide, silver bromoiodide, silver chlorobromoiodide or mixtures thereof. The emulsions used can be coarse of fine .grain and can bepreparedby any of the well-known proce- .dures,.e.g., single-jet emulsions, double-jet emulsions,

such as Lippmann emulsions, ammoniacal emulsions, thiocyanate or thioether ripened emulsions such as thosedescribed in Nietz et al., U.S. Pat. No. 2,222,264,

Illingsworth, U.S. Pat. No. 3,320,069, and McBride,

US. Pat. No. 3,271,157. Surface image emulsions can .be usedorinternal image emulsions such as those described inDavey et al., U.S. Pat. No. 2,592,250; Lowe .et1a|., U.S. Pat. No. 3,206,313; Berriman et al., U.S. Pat. No. 3,367,778;and Bacon et al., Belgian Pat. No.

704,255. {if :desired, mixtures of surface and internal :imageemulsions .canbe used as described in Luckey et al., U.S. Pat. No. 2,996,382. Negative-type emulsions .can be usedor directpositive emulsions such as those described in Leermakers, U.S. Pat. No. 2,184,013; Kendall et al., U.S. Pat. No. 2,541,472; Berriman, U.S.

The emulsions used can beunwashed or washed to remove soluble salts and the emulsions can be sensitized with chemical sensitizers. Development modifiers, antifoggants, stabilizers and developing agents can be incorporated into silver salt emulsions useful in this invention.

In addition to silver halide layers involving an emulsion, binder-freesilver halide layers are also well-suited for use in the present invention. Useful layers of this latter type include evaporated or vacuum-deposited layers of silver halide microcrystals. Such layers can be prepared by evaporating under high vacuum conditions at least one silver halide andcondensing the silver halide vapors directly onto a suitable support. Binder-free sensitive layers useful inthis invention are described further in British Pat. No. 968,453 and in U.S. Pat. No. 3,219,451. Electrically conducting polymers such as those described in Salminen, U.S. Pat. No. 3,184,311, and Minsk, U.S. Pat. No. 3,206,312, can be coated over the evaporated layers or they can be added to silver halide emulsions to enhance the imagewise transfer of information from the image-bearing member to the silver halide element. a

Preferred silver halide emulsions contain a very low concentration of, gelatin, e.g., less than about 5 grams of gelatin permole of silver.

The sensitive surface of a silver halide element as described above is placed in contact with the charged surface of the electrostatic image-bearing member. The member and element are held in contact for a time sufficient to produce a latent image on the silver halide element. A latent image is produced virtually instantaneously and generally a contact time of up to 5 seconds is sufficient to produce a latent image from even a weak electrostatic charge pattern. The element and member can simply be laid one on top of the other or they can be gently rolled into contact if desired. However, no pressure is necessary to facilitate formation of the latent image. The process of this invention is also advantageous in that no electrical connection or biasing is required between the silver halide element and the electrostatic image-bearing member.

After contacting the image-bearing member with a silver halide element to form a latent image, the element is then developed by any of a variety of techniques now well-known in the art. For example, the element bearing a latent image can be processed by various methodsincluding processing; in alkaline solutions containing conventional developing agents such as hydroquinones, catechols, aminophenols, 3- pyrazolidones, phenylenediamines, ascorbic acid derivatives, hydroxylamines, hydrazines and the like and thereafter fixed in a silver halide solvent such as watersoluble thiosulfates, thiocyanates or the like; web processing such as described in Tregillus et al., U.S. Pat.

No. 3,179,517; stabilization processing as described in Yackel et al., Stabilization Processing of Films and Papers, PSA J0urnaI,Vol. 16 B,'August, 1950; monobath processing as described in Levy, Combined Development and Fixation of Photographic Images with Monobaths, Phat. Sci. and Eng.', Vol. 2, No. 3, October, 1958; and Barnes et al., U.S. Pat. No. 3,392,019.

' If desired, the silver halide-containing elements can be processed in hardening developers such as those described in Allen et al.,U.S. Pat. No. 3,232,761; in roller transport processors such as those described in Russell, U.S. Pat. No. 3,025,779; or by surface application processing as described in Example 3 of Kitze, US. Pat. No. 3,418,132. Of course, all known development techniques for increasing effective speed can be utilized if necessary or desired as well as can heat development techniques physical development techniques, etc.

The present invention can utilize a photoconductor which has a spectral sensitivity which is completely different from the spectral sensitivity of the silver halide element. For example, an infrared-sensitive photoconductor can be used to create a latent image on a bluesensitive silver halide layer. Similarly, color images can be produced using a photoconductive layer having different spectral sensitivities in conjunction with completely unsensitized color silver halide elements. The silver halide elements are subsequently developed by standard color development processes.

It is understood that the term actinic radiation, as used herein, is not limited to visible light, but also encompasses any form of radiation capable of producing an imagewise change in charge conditon. Thus, elements can be prepared which are responsive to X-rays, gamma rays and the like to produce a charge pattern useful in the process of this invention. Similarly, the term photoconductive is not to be construed as being limited to a change in conductivity in response solely to visible light, but includes a response to actinic radiations as defined above.

The following examples are included for a further understanding of the invention.

EXAMPLE 1 An l8-gram portion of Lexan 105 polycarbonate and 12 grams of 4,4'-diethy1amino-2,2'-dimethyltriphenylmethane photoconductor are added to 200 m1. of methylene chloride. Lexan 105 is a polycarbonate resin formed from the reaction between phosgene and dihydroxydiarylalkane or from ester'exchange between diphenyl carbonate and 2,2-bis-4-hydroxyphenylpropane (General Electric Company). Additional methylene chloride is added to the above mixture to bring the total weight to 300 grams. Next, to a 25-ml. portion of the Lexan-photoconductor mixture is added 0.025 gram of sensitizing dye, anhydro-5,5,6,6'-tetrach1oro- 1,1 ',3-triethyl-3'-(3-su1fobutyl)benzimidazolocarbocyanine hydroxide, dissolved in 1 ml. of methanol to which 0.2 ml. of a percent methanol solution of ptoluene sulfonic acid has been added. The resultant mixture is then coated on a conductive paper support and dried. The coated surface of the resultant electrophotographic element is charged by subjecting it to a corona discharge in the dark. The charged element is then exposed for l/lOO of a second at a slit width of 1.0 mm. in a Bausch and Lomb Wedge Spectrograph. The resultant electrostatic charge pattern is rendered visible by cascading over the element an electroscopic toner comprised of glass bead carrier particles and toner materials formed of carbon black in a polystyrene binder. The developed image is heated to about 120 C. to fuse the toner material and thereby form a permanent image. An examination of the wedge spectrogram reveals a spectral sensitivity from 400 to 600 mm.

EXAMPLE 2 The procedure of Example 1 is repeated to the point of forming an electrostatic charge pattern. Next, the electrophotographic member bearing the electrostatic charge pattern is gently rolled in face-to-face contact with an evaporated silver bromide layer on a paper support prepared in accordance with the procedures described on pages 3 and 4 of British Pat. No. 968,453. The photographic element is then processed in the following processing composition for 45 seconds at 22 C.

water 750 ml.

N-methyl-p-aminophenol 5.0 g.

sodium sulfite 40.0 g.

sodium metaborate, 4H O 40.0 g.

hydroquinone 15.0 g.

1-pheny1-S-mercapto-tetrazole 0.1 g.

sodium thiosulfate 4.0 g.

S-methyl benzotriazole 0.38 g.

water to make 1 liter A good silver image is obtained after development.

EXAMPLE 3 A low-gelatin silver bromide emulsion as described in Example 1 of Russell, U.S. Pat. application Ser. No. 64- 2,514, filed May 5, 1967, now US. Pat. No. 3,539,344, is substituted for the evaporated silver bromide material of Example 2. The silver halide element is comprised of a poly( ethylene terephthalate) film base bearing a conventional terpolymer adhesive coat upon which is coated an aqueous gelatin solution which is chill-set and dried. The low-gel silver bromide layer is then laid down in an extremely thin coat or at a coverage of 108 mg. of silver per square foot. The emulsion contains less than 5 grams of gelatin per mole of silver and contains silver halide grains of extremely small grain size. The procedure of Example 2 is again repeated by contacting a chargeable member bearing an electrostatic charge pattern with the low-gelatin emulsion above. The photographic element is then developed in the developer composition of Example 2 to produce a good photographic image.

EXAMPLE 4 The procedure of Example 2 is again repeated using in place of the organic photoconductor-containing element an electrophotographic element comprised of a conductive support having coated thereon photoconductive zinc oxide contained in a phthalic anhydride binder vehicle. The electrophotographic element is charged and exposed and contacted face-to-face with the silver bromide layer of Example 2 which in turn is developed in the developer composition of Example 2. A photographic image results which has good quality.

EXAMPLE 5 The silver bromide layer as described in Example 2 is covered by a 0.00025-inch-thick insulating sheet of poly(ethylene terephthalate). A photoconductive grid assembly is used for applying a charge on the insulating sheet. The assembly, comprising, in order, a corona wire source, an uncoated metal grid and a photoconductor-coated metal grid, is more particularly described in British Pat. specification No. 1,152,308 published May 14, 1969, on page 12, lines 4-89, and in FIG. 14. The photoconductor-coated grid is charged in the absence of actinic radiation, and imagewise exposed. The assembly is then placed approximately oneeighth inch above the surface of the insulating sheet covering the silver bromide layer. The corona wire is again activated, whereupon a charge pattern is produced on the insulating sheet which corresponds to the imagewise charge pattern produced on the photoconductive grid in the previous step. The insulating sheet and the silver bromide layer are then stripped apart, and the silver bromide layer developed in the developer composition of Example 2. A good photographic image results.

EXAMPLE 6 The procedure of Example is followed, except that the insulating sheet bearing the electrostatic charge pattern is also developed by immersing in a liquid developer comprising marking particles of carbon black and soya oil modified alkyd resin dispersed in an electrically insulating isoparaffinic hydrocarbon carrier liq uid boiling in the range of 300 to 360 F. A visible reproduction of the image is produced, indicating that a charge pattern also remains on the insulating sheet.

EXAMPLE 7 The procedure of Example 5 is repeated, using as the charge-receiving member an insulating layer comprised of a clay subbed paper support having coated over the clay a mixture of the following ingredients at a coverage of g./ft

10.5 g. polymeric binder of a terpolymer of vinyl bu tyral (80 percent), vinyl alcohol 10 percent), vinyl acetate (2 percent) having an approximate molecular weight of about 50,000 (s uch as Butvar B-76, Plastic Products & Resins Division, Monsanto Company);

80 g. of toluene;

3.2 g. of pigmenting particles of titanium dioxide having anaverage particle size of 0.3 micron (Titanox RA, Titanium Pigments Corp.); and I 0.32 g. spacing filler particles of titanium dioxide having an average effective diameter of 7 to microns (Titanox TG, Titanium Pigments Corp.). A member having an insulating layer of the above mixture is further described in Example 1 of Graham and Robinson, U.S. Pat. application Ser. No. 673,544 filed Oct. 9, 1967 now U.S. Pat. No. 3,519,819. The photoconductive grid is imagewise exposed and is simultaneously coronacharged to produce a charge pattern on the insulating layer. The charge-receiving member is then placed in face-toface contact with the silver bromide element as in Example 2 and stripped therefrom. Upon development in the developer of Example 2,

g the silver bromide element is found to yield a good visible silver reproduction of the image. Likewise, development of the charge-reeeiving member in a liquid developer as in Example 6 yields a good visible reproduction.

This invention has the added advantage of allowing aproof to'be rapidly prepared prior to development of thelatent image on the silver halide element. After the latent image is formed, there still remains an electrostatic charge pattern on the charge-bearing member. Thus, one can rapidly develop this electrostatic charge pattern by standard electophotographic techniques. The resultant visible image thus provides a readily available lproof before the latent image is developed.

The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

We claim:

l. A process of rendering. electrostatic charge patterns visible comprising the steps of forming an electrostatic charge pattern on a surface of a charge-bearing member, placing said surface in contact with the radiation sensitive surface of a silver salt element in the absence of electrical biasing to produce a latent image on said element corresponding to said charge pattern and developing said latent image to produce a visible image. V

2. The process as described in claim 1 wherein said charge pattern is formed 'on anjelectrophotographic member comprised of a support having coated thereon a layer of a photoconductive composition comprised of at least one percent photoconductor by weight.

3. The process as described in claim 2 wherein said photoconductive composition contains an organic photoconductor.

4. The process as described in claim 1 wherein said element is comprised of a silver halide emulsion coated onto a support.

5. The process as described in claim 4 wherein said silver halide emulsion contains gelatin in a concentration of less than about 5 grams per mole of silver.

6. The process as described-in claim 1 wherein said element is comprised of a support having thereon a layer of vacuum-deposited silver halide microcrystals.

7. A method of forming visible images comprising the steps of forming an electrostatic charge pattern on a surface of a charge-bearing member, placing said surface in contact with the silver halide-bearing side of a silver halide element in the absence of electrical biasing and for a period of time sufficient to produce a latent image on said element, developing and fixing said element to produce a stable, visible image corresponding to said charge pattern.

8. A method as described in claim 7 wherein said charge-bearing member is comprised of an electrically insulating sheet. I

9. A method of forming visible images comprising the steps of electrophotographically forming an electrostatic charge pattern on an electrophotographic member comprised of a support having coated thereon a photoconductive layer comprised of at least one percent photoconductor by weight in an electrically insulating binder, placing said electrophotographic member in contact with the light-sensitive surface of a silver halide element for a period of time sufficient to produce a latent image, developing and fixing said latent image to form a stable,'visible image.

10. The method as described in claim 9 wherein said electrophotographic member has a spectral sensitivity different from that of said silver halide element.

11. The method as described 'in claim 9 wherein said silver halide element is comprised of a support having coated thereon a layer of vacuum-deposited silver halide microcrystals.

12. The method as described in claim 9 wherein said silver halide element is comprised of a support having coated thereon a silver halide emulsion.

13. The method as described in claim 12 wherein said silver halide emulsion contains gelatin in a concentration of less than about 5 grams per mole of silver.

14. A method of forming visible images comprising the steps of forming an electrostatic charge pattern on a photoconductor grid by means of a corona source, placing said photoconductive grid above an insulating sheet covering the silver salt-bearing layer of a silver salt element, reactivating the corona source to produce sheet and said silver salt element apart to produce a laa charge pattern on said insulating sheet in the absence tent image, and developing said latent image to proof electrical biasing with respect to the insulating sheet duce a visible image.

and the silver salt element, stripping said insulating 

2. The process as described in claim 1 wherein said charge pattern is formed on an electrophotographic member comprised of a support having coated thereon a layer of a photoconductive composition comprised of at least one percent photoconductor by weight.
 3. The process as described in claim 2 wherein said photoconductive composition contains an organic photoconductor.
 4. The process as described in claim 1 wherein said element is comprised of a silver halide emulsion coated onto a support.
 5. The process as described in claim 4 wherein said silver halide emulsion contains gelatin in a concentration of less than about 5 grams per mole of silver.
 6. The process as described in claim 1 wherein said element is comprised of a support having thereon a layer of vacuum-deposited silver halide microcrystals.
 7. A method of forming visible images comprising the steps of forming an electrostatic charge pattern on a surface of a charge-bearing member, placing said surface in contact with the silver halide-bearing side of a silver halide element in the absence of electrical biasing and for a period of time sufficient to produce a latent image on said element, developing and fixing said element to produce a stable, visible image corresponding to said charge pattern.
 8. A method as described in claim 7 wherein said charge-bearing member is comprised of an electrically insulating sheet.
 9. A method of forming visible images comprising the steps of electrophotographically forming an electrostatic charge pattern on an electrophotographic member comprised of a support having coated thereon a photoconductive layer comprised of at least one percent photoconductor by weight in an electrically insulating binder, placing said electrophotographic member in contact with the light-sensitive surface of a silver halide element for a period of time sufficient to produce a latent image, developing and fixing said latent image to form a stable, visible image.
 10. The method as described in claim 9 wherein said electrophotographic member has a spectral sensitivity different from that of said silver halide element.
 11. The method as described in claim 9 wherein said silver halide element is comprised of a support having coated thereon a layer of vacuum-deposited silver halide microcrystals.
 12. The method as described in claim 9 wherein said silver halide element is comprised of a support having coated thereon a silver halide emulsion.
 13. The method as described in claim 12 wherein said silver halide emulsion contains gelatin in a concentration of less than about 5 grams per mole of silver.
 14. A method of forming visible images comprising the steps of forming an electrostatic charge pattern on a photoconductor grid by means of a corona source, placing said photoconductive grid above an insulating sheet covering the silver salt-bearing layer of a silver salt element, reactivating the corona source to produce a charge pattern on said insulating sheet in the absence of electrical biasing with respect to the insulating sheet and the silver salt element, stripping said insulating sheet and said silver salt element apart to produce a latent image, and developing said latent image to produce a visible image. 